The products which did not meet the standard have been removed from Amazon's website.

A spokesman for the company said: "All Marketplace sellers must follow our selling guidelines and those who don't will be subject to action including potential removal of their account. The products in question are no longer available."

Slime from high street retailers, The Works and Smyths, which was tested also met the standard.

Which? said it has passed its findings to the Office for Product Safety and Standards.

It also warned that parents making homemade slime should be wary when considering this option.

Some reports have suggested that youngsters have sustained injuries after trying to replicate slime recipes found online.

Nikki Stopford, director of research and publishing at Which?, said: "If you have school-age kids you're probably very well aware of the latest slime craze sweeping the playgrounds. Kids love it.

"Parents buying slime for their children should have peace of mind that these toys are safe, so they will be shocked to find that the health of their children could be put at risk by these slimes.

"There must be fundamental changes to the product safety system.

"Manufacturers must stop making unsafe products and the Government and retailers simply have to do a far better job of getting anything identified as a risk off the shelves and out of people's homes".

A Department for Business, Energy and Industrial Strategy spokesman said: "The Government's top priority is to keep people safe, which is why goods being sold in the UK must meet some of the strictest safety laws in the world.

"The evidence provided by Which? will be considered by the Office for Product Safety and Standards and [it can] take any appropriate action."

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